1. Field of the Invention
The present invention relates to a solution sending pump including a pump head having a pump chamber inside itself, a plunger for reciprocating with its tip end inserted into the pump chamber, and a driving portion having a motor for driving the plunger.
2. Description of Background Technique
As a solution sending pump used for sending a solution such as mobile phase in liquid chromatograph, there is a commonly used pump formed to convert rotary movement of a motor into reciprocating movement in a certain direction by a cam mechanism to drive plungers (see Japanese Patent Application Laid-Open No. 7-318548, for example).
Tip ends of the plungers are inserted into pump chambers provided in pump heads and the solution is taken in and discharged by sliding the plungers in the pump chambers. In such a solution sending pump, the plungers, the motor, the cam mechanism are retained by a retaining member and integrated with each other. The retaining member is, for example, an aluminum die-cast product.
If a motor main body is in direct contact with the retaining member, vibration at the time of driving of the motor is transmitted to the plungers through the retaining member and influences operation of the plungers. To cope with this, blind nuts made of rubber are used to fix the motor and the retaining member while separating them from each other or a vibration absorbing rubber for absorbing vibration is sandwiched between the motor and the retaining member.
Besides the problem caused by the vibration, heat radiating effect for suppressing increase in motor temperature when the motor is driven for a long time or driven at high speed is not sufficient in the prior-art structure and the motor temperature increases to a high temperature, which reduces performance. This happens because the blind nuts or the vibration absorbing rubber interposed between the motor and the retaining member prevents transmission of heat of the motor to the retaining member, though the retaining member may have a heat radiating function. High surface temperature of the motor decreases motor longevity and performance to thereby reduce solution sending accuracy.